calcium channel

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a passage, cut, or groove through which something can pass or flow across a solid structure.
calcium channel (calcium-sodium channel) a slow voltage-gated channel very permeable to calcium ions and slightly permeable to sodium ions, existing in three subtypes designated L, M, and N and located throughout the body; calcium channels are the main cause of action potentials in certain smooth muscles, and the N channels regulate neurotransmitter release.
fast channel a protein channel, such as a sodium channel, that becomes activated relatively quickly; a fast voltage-gated channel has a much lower activation potential than does the slow type. See also slow channel.
ligand-gated channel a protein channel that opens in response to the binding of a molecule (the ligand) to the protein, which causes a conformational change in the protein molecule. See also voltage-gated channel.
potassium channel a slow voltage-gated channel selective for the passage of potassium ions, found on the surface of a wide variety of cells, including nerve, muscle, and secretory cells; its functions include regulation of cell membrane excitability, regulation of repetitive low frequency firing in some neurons, and recovery of the nerve fiber membrane at the end of the action potential.
protein channel a watery pathway through the interstices of a protein molecule by which ions and small molecules can cross a membrane into or out of a cell by diffusion; protein channels play a vital role in depolarization and repolarization of nerve and muscle fibers, and may have physical characteristics such as shape or diameter that particularly attract certain ions.
slow channel a protein channel such as the calcium channel that is slow to become activated; a slow voltage-gated channel has a much higher activation potential than does the fast type. See also fast channel.
sodium channel a type of fast channel selective for the passage of sodium ions. Voltage-gated sodium channels are the main causes of depolarization and repolarization of nerve membranes during the action potential. In cardiac cells they produce phase 0 of the action potential.
voltage-gated channel a protein channel that can be opened or closed in response to changes in the electric potential across a cell membrane. See also ligand-gated channel.
water channel a channel in a cell membrane that permits passage of water molecules; chemical substances such as vasopressin cause the opening of new channels and increase permeability.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

calcium channel

A family of transmembrane ion channels—most of which are voltage-gated, some of which are ligand-gated—which release Ca2+from stores in skeletal muscle, cardiac muscle, bone and neurones.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.
References in periodicals archive ?
Calcium signalling through L-type calcium channels: role in pathophysiology of spinal nociceptive transmission.
Despite the fact that verapamil is most frequently used, it still have certain limitations such as it has lesser vasodilator property of radial artery as compared to other calcium channel agonists.16
[20] The anticonvulsant effect of nifedipine may also be correlated with the increase in local blood flow due to vasodilatation, [21] and all these effects of nifedipine may be due to central blockade of calcium entry through dihydropyridine L type calcium channels. [8] It has been established that even small alterations in the biophysical properties of presynaptic calcium channels could have a significant impact on the firing properties of nerve cells and neuronal networks with the potential to lead to epileptic seizure activity.
Calcium channel blockers such as amlodipine and cilnidipine are very effective antihypertensive agents by virtue of their action on L-type calcium channels present in the vascular smooth muscles.
Calcium channel blockers (CCBs) are among the most frequently prescribed drugs for the treatment of cardiovascular diseases like hypertension, angina pectoris, cardiac arrhythmias, left ventricular diastolic dysfunction, Raynaud's phenomenon, etc.1 The main effect of CCBs is vasodilation with lowering of the blood pressure.
Aside from standard cardiopulmonary measures in calcium channel blocker overdoses, additional commonly employed resuscitative therapies have included gastric lavage, multi-dose oral or nasogastric activated charcoal, flumazenil infusion, naloxone infusion, insulin and glucagon intravenous boluses, continuous calcium gluconate infusion, intravenous antiarrhythmics as indicated, and vasopressor support during mechanical ventilation.
Calcium channels, selective gates in neuron walls, are integral in neuron firing, ensuring that all parts of the brain keep talking to one other.
Calcium channel blocking agents like verapamil, nifedipine and diltiazem are commonly used in the treatment of hypertension, angina, myocardial infarction and supraventricular tachycardia.6 Induction of hypercalcaemia through intravenous administration of calcium, is usually associated with increased gastric volume and acidity.7,8 The acid stimulating ability of calcium; is well known and there is extreme sensitivity to calcium in patients with Z-E syndrome.9,10 Calcium channel blocker Verapamil may interfere with H+K+ ATP ase due to its high affinity for the site H+K+ATP ase system which is accessible from luminal side of the stomach.11
The major disadvantage is cost but there are generic ACE-inhibitors and calcium channel blockers on the market, which helps.
Experiments demonstrating that a specific calcium channel is necessary for LTP or LTD suggest that calcium is required in a specific location.
Researchers from the Fred Hutchinson Cancer Research Center recently conducted the only long-term study on calcium channel blockers for hypertension.
During five years of follow-up, beta-blockers were prescribed to 915 patients, diuretics to 1 316, statins to 1 353 and calcium channel blockers to 1 171.

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